1.(Field of the Invention)
The present invention relates to a work alignment apparatus for double-sided exposure of a work, such as a printing board, adapted to align image masks and the work when two opposite sides of the work are exposed simultaneously to images of printed wiring or the like.
2. (Description of the Prior Art)
In printing a predetermined image, such as a wiring pattern, on a work, e.g., a printing board, by exposure, mask films are located close to and in alignment with the work and parallel beams of light are applied to the work through the mask films. "A method of printing on a printing board" is disclosed in Japanese Patent Application No. 055708/61 filed on Mar. 13, 1986 by the inventor hereof. This prior art method is associated with a method of aligning upper and lower surface mask films and a work, such as a printing board, before simultaneously exposing both sides of the work. In this method of alignmemt between the work and the mask films for the simultaneous double-sided exposure, the work is first set in an exposing position. Then, a printing frame which holds the upper-surface mask film is positioned with respect to the work by viewing reference marks for positioning on the work and the mask films. Thereafter, a printing frame which holds the lower-surface mask film is positioned in the same manner as the first or upper printing frame.
According to the prior art method described above, however, alignment mechanisms must be provided individually for the upper- and lower-surface mask films. These mechanisms adjust the positions of the mask films with respect to two directions (X- and Y-directions) which intersects at right angles on a plane and with respect to a rotational direction (.theta.-direction) of the plane in accordance with misalignments between the reference marks on the printing board and the mask films. Thereafter, the mask films, along with the alignment mechanism itself, must be brought in position close to the printing board with high accuracy, thus requiring a highly complicated arrangement. This causes a high cost. Further, the use of the separate alignment mechanisms for the two upper- and lower-surface mask films, as well as the complicated arrangement thereof, entails a substantial increase in cost of the apparatus.